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Lift vs Droop for various open length struts on Prado 120 IFS

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  • Lift vs Droop for various open length struts on Prado 120 IFS

    Hey everyone,

    I thought this plot deserved to have its own thread to get more exposure and to show everyone the IFS leverage ratio at work.

    The plot below shows lift (inches) vs droop for struts with different open lengths.



    The dashed lines have been created by using the leverage ratio of 1:2.12 (measured on my Prado). As such, a 10mm increase in strut open length translates to 21.2mm increase in droop. I've assumed that the coil seat location doesn't change between different struts, which I cannot presently confirm. If the seat position does change, then this will change the coil pre-load and the resultant lift, however, I don't think there will be much difference in seat position, perhaps only a few mm.

    These lines are also for factory UCA's only, which will typically contact a coil at full droop on long struts. Using after market UCA's will improve the droop, and on fully open 570mm struts, you may get very close to binding the CV.

    The solid circles are real lift and droop data points measured from different struts.

    As the most popular lift is typically 2", to maintain a minimum droop of 60mm, you need to run a strut with open length of 558mm.

    I personally believe the widely quoted figure of minimum 60mm droop is misleading, as I can get my short open length 712 struts to top out on roundabouts/speedbumps with 75mm droop at 1" lift.

    To maintain close to 75mm droop at 2" lift, you need to run around a 564mm strut. The OEM strut/coil has 95mm droop at 0" lift at 750mm ride height.

    Best

    Mark
    Whitey
    Shockie Maker of the Month Award
    Last edited by Whitey; 20-09-2017, 03:35 PM. Reason: Plot update
    2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

  • #2
    I run the 712 and have kings standard raised springs, set on the bottom notch. Steel bar, winch and second battery.
    Don't have the same issue as yourself with the struts extending to bump stop. Have done a lot of off-road but always on the caution side, and no full droop bump other than when lifting wheels. Haven't measure the droop on mine but will do next time I get the jack out.

    Rusty.
    08 VX D4D, Lift, Safari Snorkle, Trailblazer Fridge, Custom Storeage System, BFG, ARB Safari Bar, Wife, Kids, Codan NGT HF Radio, Debt.
    06 100 Series Sahara, Bilteins, Kings, Beaudesert 3", Diff drop, Unichip Q4, Safari Intercooler, EGR delete, 20ft Bushtracker, Codan Envoy more coming.
    Sometimes i wake up Grumpy, most times i leave her sleep.

    Comment


    • #3
      Hey Rusty,

      That's interesting, maybe the higher spring rate (660lb/in) King coils mask the topping out a bit. My Ridepro coils are 612lb/in, and have sagged at least 2mm and have prolly lost some spring rate as well.

      With steel bar, winch and secondary battery on standard kings, I'm guessing you're sitting around 0.8-1" lift and maybe 75mm droop.

      The two points on the 712 line are for a factory vehicle with no accessories, bullbar came later. I'm down to around 1" lift now with 75mm droop with an ARB deluxe bar.

      Be interesting to hear your lift and droop figures!

      Best

      Mark
      2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

      Comment


      • #4
        Thanks for posting up the useful info.

        I'm not too happy with my current front struts. Droop is good but I'm getting coil bind before hitting bump stops. Not good.

        I'm planning to get some Lovells 64610087F shocks as they have good open and closed lengths. I was talking to a vendor and suggested to him that I wanted the standard raised springs and would use the strut coil spacers to adjust height (similar to moving the clips up and down on Bilsteins). He said that doing this would reduce the amount of available droop.

        I can't understand how this would affect droop. It should only affect coil pre-load and hence height. It might cause coil bind but shouldn't affect the open length. Am I missing something?

        He wanted to sell me HD springs but I'd rather the lower spring rate for comfort. I'll use the spacers to adjust the height. I only have a dual battery up front.

        Comment


        • #5
          Are you talking strut spacers or coil spacers? Strut spacers go on top of the strut cap and will not affect droop but will give lift. Coil spacers on the other hand go between the coil and strut cap, these will reduce droop by the thickness of the spacer.

          Cheers Andrew
          [COLOR="#FF0000"]So Long and Thanks for all the Fish![/COLOR]

          [url=http://www.4wdadventurers.com/showthread.php?3840-AJ-s-120-Prado]MY PRADO AND DIY CAMPER TRAILER[/url]

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          [SIGPIC][/SIGPIC]

          Comment


          • #6
            They are spring seat spacer and go installed on the bottom of the spring which is like lifting the spring seat.

            Still can't get my head around how a spacer between the coil and strut cap can reduce droop. Wouldn't the open length of the strut remain unchanged even with the spacer installed? My understanding is droop is a function of the open length of the strut.

            Comment


            • #7
              Had a think about it and I agree that coil spacers will reduce droop. The open length of the strut will determine the lowest position of the wheel. Droop is the amount of travel from resting position to lowest position of the wheel.

              So by increasing the pre-load on the spring with spacers there will be lift causing the wheel to sit lower in the wheel arch which means we have less downward available travel and hence less droop.

              If the spacer is on the top of the strut cap this will essentially move the entire strut down which changes both resting position of the wheel and the fully extended position of the wheel. Hence we get lift and no change in droop. However we need to be careful of CV and UCA bind if wheel position is too low. Also need to be careful of bottoming out the shock and may require spacing down the bump stops.

              So any type of lift will affect droop if the open length of the strut does not change. To increase lift and maintain or increase droop we need to have a strut with a longer open length.

              Let me know if I got anything wrong.

              Comment


              • #8
                I think you have all that spot on now.

                Buying a new set of springs with the intention of adding a coil spacer is a bit pointless, you may as well just get a longer spring to begin with.

                I am a bit biased as I make and sell strut top spacers, but at least then can be added after your coil is fitted if you find your lift is not quite what you wanted, and they don't reduce droop like a coil spacer or longer spring.

                The larger the strut spacer the more likely they will cause issues, I run 6mm spacers in my 120 for around 12mm extra lift and didn't need to adjust anything else.

                Cheers Andrew

                Cheers Andrew
                [COLOR="#FF0000"]So Long and Thanks for all the Fish![/COLOR]

                [url=http://www.4wdadventurers.com/showthread.php?3840-AJ-s-120-Prado]MY PRADO AND DIY CAMPER TRAILER[/url]

                [url=http://www.4wdadventurers.com/showthread.php?3975-AJ-s-79-series-Cruiser-Ute]MY HZJ79 Landcrusier[/url]


                [SIGPIC][/SIGPIC]

                Comment


                • #9
                  Originally posted by Tin175 View Post
                  Had a think about it and I agree that coil spacers will reduce droop. The open length of the strut will determine the lowest position of the wheel. Droop is the amount of travel from resting position to lowest position of the wheel.

                  So by increasing the pre-load on the spring with spacers there will be lift causing the wheel to sit lower in the wheel arch which means we have less downward available travel and hence less droop.

                  If the spacer is on the top of the strut cap this will essentially move the entire strut down which changes both resting position of the wheel and the fully extended position of the wheel. Hence we get lift and no change in droop. However we need to be careful of CV and UCA bind if wheel position is too low. Also need to be careful of bottoming out the shock and may require spacing down the bump stops.

                  So any type of lift will affect droop if the open length of the strut does not change. To increase lift and maintain or increase droop we need to have a strut with a longer open length.

                  Let me know if I got anything wrong.
                  Excellent explanation, you've got it all under control!

                  Best

                  Mark
                  2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

                  Comment


                  • #10
                    Originally posted by Tin175 View Post
                    I'm not too happy with my current front struts.

                    I'm planning to get some Lovells 64610087F shocks as they have good open and closed lengths.
                    Hey Tin,

                    Be aware that Lovells are on to generation III of the gas legends, and that the Lovells 64610087F (Gen I) 420-570mm strut no longer exists and cannot be purchased anywhere.

                    You can however purchase a modified Hilux strut (24.T4041) from Driveline services in Brisbane who are the original creators of the Gen I struts/shocks, which Lovells bought and sold with a Lovells sticker.

                    As the coil seat sits 5mm lower on a Hilux strut compared to a Prado 120 strut, you'll need a 5mm coil seat collar, which they'll machine up for you.

                    I'm currently running the modified Hilux strut with a 5mm collar and closed-open length 420-570mm.

                    Best

                    Mark
                    2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

                    Comment


                    • #11
                      Originally posted by Tin175 View Post
                      I'm not too happy with my current front struts. Droop is good but I'm getting coil bind before hitting bump stops. Not good.
                      I think it's highly unlikely you're getting coil bind. How have you determined this?? What closed-open length strut are you currently running, and what is the free height of your coils? You can work out the solid coil length easily from the thickness and number of coil windings.

                      Take a look at the second plot in this thread;

                      http://www.pradopoint.com/showthread...-Prado-120-IFS

                      With a typical after market Prado coil, you can't get solid coil until you're at the end of bumpstop compression.

                      I think something else is going on, so again, how do you think you're getting solid coil? Can you put a go pro or something down in the wheel arch to show me?

                      Best

                      Mark
                      2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

                      Comment


                      • #12
                        Originally posted by Whitey View Post
                        I think it's highly unlikely you're getting coil bind. How have you determined this?? What closed-open length strut are you currently running, and what is the free height of your coils? You can work out the solid coil length easily from the thickness and number of coil windings.

                        Take a look at the second plot in this thread;

                        http://www.pradopoint.com/showthread...-Prado-120-IFS

                        With a typical after market Prado coil, you can't get solid coil until you're at the end of bumpstop compression.

                        I think something else is going on, so again, how do you think you're getting solid coil? Can you put a go pro or something down in the wheel arch to show me?

                        Best

                        Mark
                        I'm pretty certain that my coils will bind before hitting the bump stops. I'm running a Profender OEM 2.0 adjustable coil over. The springs are a smaller diameter than the standard springs and even with the HD springs with a 2" lift there is not much room between the coils.

                        The shocks are fine and have an open length of about 20mm longer than stock. (approx 570). The problem is there is not much of a choice of springs. What it really needs is a spring with a longer free length so I don't have wind down the pre-load nut so much. Looking back, I should have bought a strut that uses the standard style springs.

                        Here are a couple of pictures with the back corner of the car backed up on a hill until I have 2 wheels lifted. This puts the weight on the front corner. I pretty much have solid coil but still have about 10mm til the bump stop touches let alone compresses.


                        Comment


                        • #13
                          Hey Tin,

                          Holy moly, I believe you now!

                          That does not look good at all.

                          The non-standard coil on the Profender explains everything. I have a few thoughts on this that might help you get a solution;

                          1. What lift are you running on the front end?? Just wondering how far down the top adjuster is wound?

                          2. Can you calculate the length at which solid coil bind is occurring for that non-standard coil, it's straight forward, you just need the thickness and number of windings according to the following;

                          http://www.acxesspring.com/solid-height.html

                          You can prolly also repeat what you did in the photos, and just measure the bound coil to compare to the calculated solid length.

                          3. Did you buy the Profenders through Superior?

                          I'm wondering if the Profender has the same outer diameter as the Amada, as with the Amada's you can run standard type coils like Dobinsons.

                          If the diameters are the same, I would be going straight to Superior, showing them your photos with coil bind, and the calculated solid coil length, and see if they can re-engineer the coil seat and the adjuster hat so that you can put some Dobinsons in.

                          Superior can make just about anything, so if they tell you they can't fix it, then I'd say you're unfortunately looking at new struts to get back to more standard type coils.

                          Just on a side note, how have the Profenders felt when you've driven without coil bind??

                          Best

                          Mark
                          2006 GXL petrol auto. ARB deluxe bar x3 HID IPF's, ARB alloy roofrack, ARB awning, BFG A/T, Safari snorkel, Piranha breathers, Pacemaker extractors, custom Ironman 45710FE 436-569mm with Dobinsons 350, custom Ironman 45682FE 383-618mm with Dobinsons 487, Firestone kevlar 60psi airbags, 30mm extended Roadsafe links, AMTS bashplate and recovery points, ABR Flyer with Powersonic AGM.

                          Comment


                          • #14
                            I'm running a 40mm lift on the front. 750 bottom of rim to arch before lift. 790mm currently. Struts are 575 long and I get 890 droop with no binding of the CV's. I have a 150 Prado.

                            I haven't had a chance to coil length. I've sourced a set of Bilsteins and springs that I will use in the meantime. At least I know I won't get coil bind.

                            I bought the Profenders through superior. The original springs that came with the strut sagged back to original height after a couple of months and I was going to get too much coil bind if I adjusted it anymore. I contacted superior and they send me some HD springs that were better but I'm still getting coil bind before bump stop. What I need is a spring with more free length. Another 30 to 40mm would be good. As far as I know they don't have any other springs for this strut. They told me that I was the first to have this problem. I have noticed that they only advertise that these struts are good for 2" lift where as when I bought them they were advertised as being good for upto 4" lift.

                            I don't mind the Profender shocks. Good build quality and solid design. Much firmer ride than stock, more controlled and less roll and diving. Can't really compare to anything else yet. I'll comment more once I get the Bilstiens in.

                            I do like the look of the Profender front struts with remote reservoir and adjustable compression damping. Would have been the about same price as my current struts when you add price of springs. Good thing is that is uses standard springs. Will probably go down this path eventually.

                            Comment


                            • #15
                              Just put together some Bilstien struts and I just discovered that not all strut tops are made the same.

                              I bought a set of second hand struts and springs and assembled them with some aftermarket strut tops. The A712 and standard 150 strut have pretty much the same open length. I put it up against the standard strut and I my open length is 20mm longer?????




                              The aftermarket top hat is not as "deep" as the factory one and essentially lowers the strut 20mm. This is like using 20mm of strut spacers. This now gives me a open length of about 570mm which is good. However I am concerned that the effective closed length is now 20mm longer which may mean the shock will bottom out before the bump stop.

                              Does anyone know the safe maximum closed length for a 150 Prado? Anyway, I'll be doing some measuring open and closed travel when the strut is out just to be sure.

                              I checked the label on the strut top and it definitely says for Prado 120/150.

                              Comment

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